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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

18515 results found.

  1. EP250321A: COLIBRÍ Optical Observations
  2. EP250321a: REM optical/NIR afterglow detection
  3. EP250321a: TRT optical counterpart detection
  4. EP250321a: Einstein Probe detection of an X-ray transient
  5. GRB 250321A: GOTO optical upper limits
  6. GRB 250314A: Keck/NIRC2 J-band upper limit
  7. EP250226a/GRB 250226A: KAIT optical observations
  8. GRB 250321A: Swift detection of a burst
  9. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  10. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  11. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  12. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  13. GRB 250314A: ATCA radio upper limits
  14. GRB 250317C: SVOM/GRM observation of a long burst
  15. GRB 250317B: Leavitt Observatory optical upper limit
  16. GRB 250309B/AT2025dws: further ATCA observations
  17. GRB 250317B: Mondy AZT-33IK Optical Observations
  18. GRB 250317C: AstroSat CZTI detection
  19. GRB 250317B: NOT optical observations suggest an optical plateau phase
  20. GRB 250317B: OHP/T193 optical observations
  21. GRB250312A: Swift/UVOT Upper Limits
  22. GRB 250317B: REM optical/NIR observations
  23. GRB 250316A: Swift/UVOT Upper Limits
  24. GRB 250314A: REM optical/NIR upper limits
  25. GRB 250316A: AbAO AS-32 Optical Upper Limit
  26. EP 250317B: Fading optical counterpart detection by LCO
  27. GRB 250316A: Swift-XRT afterglow detection
  28. GRB 250317B: LCO detection of the fading optical afterglow
  29. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  30. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  31. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  32. GRB 250317B: SVOM detection of a burst
  33. GRB 250314A: SVOM/GRM analysis
  34. The EP-WXT trigger 01709132801 is likely a flaring star
  35. GRB 250314A: EP-FXT afterglow detection
  36. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  37. GRB 250314A: Swift/UVOT Upper Limits
  38. GRB 250314A: Swift XRT Detection
  39. EP250315a: optical counterpart candidate detected by Gemini North
  40. EP250315a: Einstein Probe detection of an X-ray transient
  41. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  42. SVOM/MXT upper limit on GRB 250314A
  43. GRB 250314A: SVOM/VT upper limit
  44. GRB 250314A: NOT near-infrared candidate counterpart
  45. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  46. GRB 250314A: SVOM detection of a burst
  47. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  48. EP250304a: Pan-STARRS r and i-band imaging and photometry
  49. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  50. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  51. EP250311a/GRB 250311A: EP-FXT follow-up observation
  52. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  53. GRB 250312A: Enhanced Swift-XRT position
  54. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  55. GRB 250312A: Swift detection of a burst
  56. GRB 241213A: VIRT Optical Upper Limit
  57. GRB 241228A: VIRT Optical Upper Limit
  58. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  59. GRB 250309B: 1.3m DFOT Optical observations
  60. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  61. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  62. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  63. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  64. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  65. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  66. GRB 250309B: PRIME near-infrared detection
  67. GRB 250225B: Swift-BAT refined analysis
  68. GRB 250311A/EP250311a: TRT optical upper limit
  69. EP250311a/GRB 250311A: EP-WXT detection
  70. The EP-WXT trigger 01709132425 is not a real source
  71. GRB 250309B / AT2025dws: further SAO RAS optical observations
  72. EP250308a: 1.6m Mephisto optical upper limits
  73. IPN triangulation of GRB 250308A (short)
  74. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  75. GRB 250309B / AT2025dws: SAO RAS optical observations
  76. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  77. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  78. IceCube-250309A: No candidates from the Zwicky Transient Facility
  79. IceCube Alert 250309.32: Global MASTER-Net observations report
  80. EP250308a: Global MASTER-Net observations report
  81. EP250308a: Einstein Probe detection of an X-ray transient
  82. EP250308a: NOT optical upper limit
  83. GRB 250309A: Fermi GBM Final Real-time Localization
  84. The EP-WXT trigger 01709132387 is likely a flaring star
  85. EP250304a: MeerKAT detection of a possible radio counterpart
  86. EP250302a:Xinglong optical observations
  87. GRB250101A: Radio upper limits from VLA observations
  88. GRB 250305A: SVOM/GRM observation of a burst
  89. The EP-WXT trigger 01709132323 is likely a flaring star
  90. EP250302a: Optical Observations at CrAO and SAO RAS
  91. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  92. EP 250304A: Optical counterpart detection by LCO
  93. EP250302A: 1.3m DFOT optical afterglow detection
  94. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  95. EP250304a: REM NIR upper limits
  96. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  97. EP250302a: Mondy Continued Optical Observations
  98. EP250304a: TRT optical counterpart detection
  99. EP250304a: Einstein Probe detection of an X-ray transient
  100. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits

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